Cytolytic and Phospholipase C Activity in Legionella Species

Departments of Internal Medicine and Microbiology, Southwestern Medical School and Southwestern Graduate School of Biomedical Sciences, The University of Texas Health Science Center at Dallas, 5323 Harry Hines Boulevard, Dallas, Texas 75235, USA ABSTRACT To examine one possible mechanism of damage to leucocytes and tissue cells in legionellosis, seven species of Legionella were examined for cytolytic activity and for elaboration of phospholipase C. an enzyme that can damage mammalian cell membranes. Cytolysis was assessed using erythrocytes in agar. Phospholipase C was assayed by release of p -nitrophenol from p -nitrophenylphosphorylcholine and of tritiated phosphorylcholine from L- -dipalmitoyl-[ choline-methyl -3 H]phosphatidylcholine. L. pneumophila, L. bozemanii, L. micdadei, L. dumoffii, L. gormanii, L. longbeachae and L. jordanis all lysed dog red blood cells, which have a high ratio of membrane phosphatidylcholine to sphingomyelin. The same strains hydrolysed varying amounts of p -nitrophenylphosphorylcholine; L. bozemanii exhibited the greatest activity. L. pneumophila, L. bozemanii, L. dumoffii, L. longbeachae and L. jordanis , but not L. micdadei , released tritiated phosphorylcholine from labelled substrate. These results indicate that several species of Legionella possess cytolytic capability; exotoxins with phospholipase C activity may play a role.